1. Technical Field
The present invention relates to an electrostatic discharge preventing device for light emitting diodes (LED) for backlighting a liquid crystal display (LCD). In particular, the invention relates to an electrostatic discharge preventing device in which one electrostatic preventing circuit is provided at one printed circuit board on which LEDs are mounted.
2. Description of the Related Art
An LCD device may display an image by using an optical anisotropy characteristic of a liquid crystal. When light is irradiated onto liquid crystal having a polarized characteristic according to an applied voltage, the liquid crystal is aligned. The LCD device displays an image by controlling an amount of light passing through the liquid crystal according to an aligned state of the liquid crystal.
The LCD device comprises a liquid crystal panel containing liquid crystal between two substrates, and a driving circuit provided at a peripheral portion of the liquid crystal panel for applying a signal to the liquid crystal panel and controlling the signal. Because the liquid crystal panel is not a spontaneous display device, an additional optical source such as a backlight is required.
As a backlight for an LCD TV, a fluorescent lamp may be used. The fluorescent lamp may comprise a direct type and a light guide plate type. Also, a white LED may be used as a backlight for a small LCD device applied to a personal digital assistant (PDA), a portable phone, a notebook, or other mobile devices.
When the LEDs are fabricated, static electricity is generated to be introduced into the LEDs and may damage them. Accordingly, an electrostatic preventing apparatus for protecting LEDs from static electricity is required.
FIG. 1 shows an electrostatic preventing apparatus For LEDs for backlighting in accordance with the related art. As shown, one LED chip 11 is installed on LED package 10 to mute static electricity introduced into the LED chip 11 by a zener diode 12, thereby protecting the LED chip from static electricity.
Recently, an RGB LED chip for backlighting may be applied not only to a PDA, a portable phone, or a notebook, but also to a large display device such as an LCD TV. The RGB LED chip can reproduce more colors than the related art CCFL backlight, and can reproduce colors that are obtained with difficulty by a cathode ray tube (CRT), a plasma display panel (PDP), or a surface conduction electron emitter (SED) display.
FIG. 2 shows an inner structure of an RGB package. As shown, RGB LED chips 21, 22, and 23 are formed in one RGB package 20. A general backlight for an LCD device supplies white light to a liquid crystal panel under a turned-ON state. However, in a Field Sequential Color (FSC) LCD device, the RGB LED chips 21, 22, and 23 are sequentially driven with a period to supply white light to an liquid crystal panel.
When an RGB package for an FSC LCD is fabricated, RGB LED chips have to be installed in a limited space and may cause a difficulty in obtaining a space for installing an electrostatic preventing circuit. Furthermore, when the RGB LED chips are mounted on a surface of a flexible printed circuit board (FPCB), static electricity is generated thus to damage the RGB LED chips and thereby to degrade yield.